This invention relates to fluidized bed combustors and gasifiers, more particularly to an improved circulating fluidized bed. A practical multistaging configuration is incorporated to a circulating fluidized bed. It expands its scope of fluidized bed applications from coal to other fuels which contrary to coal, break down into volatiles upon heating. The present invention regards incineration of hazardous waste in an environmentally acceptable manner and gasification of biomass/wastes producing a low tar gas at lower cost.